libcage.h

#ifndef _LIBCAGE_H_
#define _LIBCAGE_H_

#include <stdint.h>
#include <stdio.h>

/* The implemented version of age. An arbitrary string.
*/
#define CAGE_AGE_VERSION "v1"

#define CAGE_RAW_PK_LEN 32

/* Raw bytes of an X25519 keypair.
*/
struct CageX25519Identity {
    uint8_t public_key[CAGE_RAW_PK_LEN];
    uint8_t secret_key[32];
};
/* An X25519 keypair in the standard human-readable age representation.
*/
struct CageHumanReadableX25519Identity {
    uint8_t public_key[63];
    uint8_t secret_key[75];
};

/* Returns a new X25519 age identity from a 32-byte scalar _scalar_ used as the private key. */
struct CageX25519Identity cage_new_x25519_identity_from_scalar(const uint8_t scalar[32]);
#if defined(__linux__) || defined(__FreeBSD__) || defined(__APPLE__)
/* Assigns a new X25519 age identity to _kp_.
 * On error, non-zero is returned, and errno is set to indiciate the error.
 * This function only fails if the system's CSPRNG fails to retrieve suffient entropy.
 * This function only exists on platforms with an established standard CSPRNG.
 */
int cage_generate_x25519_identity(struct CageX25519Identity *kp);
#endif
/* Parses a bech32-encoded age private key into an X25519 identity.
 * On error, non-zero is returned, and errno is set to indicate the error.
 * In particular, ENOTSUP is returned if the HRP is not "AGE-SECRET-KEY-"
 */
int cage_parse_x25519_identity(struct CageX25519Identity *out, const char bech32_sk[75]);
/* Returns the standard human-readable age representation of an X25519 keypair.
 * _kp_ MUST be a valid keypair.
 */
struct CageHumanReadableX25519Identity cage_format_x25519_identity(
    const struct CageX25519Identity *kp);
/* Decodes an X25519 public key in human-readable format into raw bytes.
 * _out_ MUST be at least 32 bytes.
 * On error, non-zero is returned.
*/
int cage_decode_x25519_pk(uint8_t *out, const char *pk);

int cage_encrypt_file(FILE *in, FILE *out, const int recipients_len, uint8_t *const *recipients);
#endif